It is known to provide an inflatable restraint system in a vehicle for restraining a vehicle occupant. In some vehicles, the inflatable restraint system may be a passenger air bag system disposed within an occupant compartment in the vehicle in close proximity to either a driver occupant or one or more passenger occupants. Typically, the passenger air bag system includes a passenger air bag module attached to an instrument panel of the vehicle and having an air bag for deployment through an opening in the air bag module to extend in an occupant compartment of the vehicle. The deployed air bag typically interacts with the occupant during a collision.
It is also known to provide one or more vent openings in walls of the air bag to vent inflation gas from an interior of the air bag into the occupant compartment. These air bag vents are commonly provided in a base wall portion of the air bag to direct the vented gas away from the occupant. The vent opening may be provided by a gas permeable fabric panel sewn into the bag. In addition, it is known to employ various flow control devices to control the flow of inflation gas through the vent opening.
It is also known to provide a displacement responsive air bag vent. An example of such a displacement responsive air bag vent is disclosed in U.S. Pat. No. 5,280,953 to Wolanin et al. In this patent, a closure valve is associated with a vent opening in the air bag for selectively venting a portion of the inflation gas into the occupant compartment. A tether located in the air bag has a first end operatively associated with the closure valve and a second end attached to the air bag so that the inflation of the air bag pulls the tether to close the closure valve and contain the inflation gas within the air bag.
As a result, it is desirable to provide tether actuated venting for a frontal air bag system. It is also desirable to provide very large vents in a housing of an air bag module for the inflation gas to escape if an occupant is seated in close proximity to the air bag module. It is further desirable to provide full deployment of a frontal air bag when the occupant is normally seated. It is still further desirable to reduce the amount of venting for a normally seated occupant to a normal amount. Therefore, there is a need in the art to provide an improved frontal air bag system.